KING OF THE ARCADE CLONE
The BBC Micro was home to dozens of fantastic coin-op conversions that belied its scholarly background. Martyn Carroll speaks to a number of well-known coders to find out why the Beeb was a good fit for faithful arcade clones
he BBC Micro was always a studious machine. It was expensive: the preferred Model B cost as much as £399 in 1982, which was around three times more than competing micros, like the Commodore VIC-20 and Sinclair Spectrum. It was educational: Acorn designed the machine for the BBC’S Computer Literacy Project and off the back of that BBC
Micros infiltrated classrooms up and down schools of the UK. As such, a huge amount of education software was developed for the machine.
The BBC Micro might have been expensive and educational, but it certainly wasn’t elitist.
Many games were available too, of course, and a number of influential masterworks like Elite,
Exile and The Sentinel began life on the system. Furthermore, the Beeb wasn’t just about weighty titles that created whole worlds inside 32K of memory – it was also adept at running pure arcade games based on the hit coin-ops of the day. If you wanted to play an authentic game of Space Invaders, Pac-man, Donkey Kong or Frogger at home then you were in luck. In fact, you could argue that no other computer could replicate the golden age of arcades with quite the same verve, assurance brilliance as the Beeb.
Despite its academic leanings, the BBC Micro was a good platform for arcade-style games. Programmer Kevin Edwards coded the Galaxian/ Galaga clone Galaforce for Superior Software and he appreciated the performance and flexibility that the hardware offered. “It was equipped with a fast, 2MHZ 6502 CPU which gave the machine a lot of horsepower,” he says. “This was important as it didn’t have any hardware sprites. In addition to this, it had a custom video ULA and 6845 display controller that gave the user lots of different graphics modes to choose from. Some were low resolution, with four or 16 colours, and others were higher resolution, but only supported two colours. All of these modes were bitmapped, rather than character-based, which allowed every screen pixel to be changed independently without limitation – perfect for writing 3D wireframe or shaded games. The 6845 also allowed you to do horizontal hardware scrolling that was perfect for porting games such as Defender and Scramble.”
Jonathan Griffiths concurs, having developed the faithful Scramble clone Rocket Raid for Acorn’s software division, Acornsoft. For him the ability to produce pixel-perfect animation and smooth scrolling was key. “The double-buffered RAM meant that the screen access was interleaved with the processor access,” he says, “so the software could read and write to the screen memory whenever it wanted without having to worry about screen glitches. And then the 2MHZ 6502 was fast enough to keep up with the screen refresh, as long as the software was written efficiently. One of the things I did in Rocket Raid was set up a timer in the 6522 support chip to tell me the vertical position of the electron beam used in the TVS and monitors, so I could ensure I only redrew the graphics that weren’t too close to the beam and avoided the occasional ‘tearing’ of sprites. Also, the ULA for colour handling and the 6845 for screen resolution and position meant that the colours of the arcades could be replicated, which made things easy.”
Praise for the BBC’S colour palette is something that Matthew Atkinson echoes. Matthew, who would go on to develop the all-time Beeb
It was equipped with a fast, 2MHZ 6502 CPU which gave the machine a lot of horsepower Kevin Edwards
classic Repton 3, wrote the official conversion of Tempest for Atarisoft (although it was ultimately published by Superior Software after Atarisoft abruptly quit the Acorn scene). He says, “Tempest is a colourful game that looks best with a full eight-colour display, something the BBC was good at. Other computers used colour screen attributes which didn’t work as well. If you look at other 8-bit conversions – including my own one for the Acorn Electron – they look a bit drab in comparison. A phrase I came across recently is ‘always choose colour over resolution’. Most of the early Atari arcade games used a 1MHZ 6502 with various hardware enhancements to assist the display. The BBC had a 2MHZ 6502 which gave you some extra power to try and emulate the arcade hardware.”
Matthew also praises the machine’s sound chip which was capable of emulating the zaps, pings and crashes that accompanied your typical arcade game. “The sound on the BBC was comparable to other 8-bit computers that used more advanced sound chips. The downside was the amount of processing power used to service the sound generation, something that was done more in hardware on other machines.”
nother Beeb aficionado is programmer Peter Johnson. He began his career writing arcade clones for the machine, including Q*bert and Deathstar (a version of Sinistar) for Superior Software, before moving over to other systems. He’s well placed to discuss the BBC Micro hardware compared to its contemporaries. “The BBC Micro eclipsed the Spectrum in terms of technical capabilities,” he states. “The C64 had other advantages that the Beeb couldn’t match, such as hardware sprites and scrolling, although the Beeb’s processor was twice as fast to compensate. Another difference was a brighter colour palette. To me, many C64 games appeared a bit washed out – although I would have loved to have had a few more shades to pick from than the eight true colours the Beeb was limited to. Skin tone choices were limited to yellow, magenta, pure black or pure white, for instance, so realism was out of the window. This probably influenced the style of games we saw on that platform, as it favoured the abstract style.”
Peter also recalls the novelty of making the Beeb ‘speak’. “Add-ons like the speech system were fun. Voiced by newsreader Kenneth Kendall, it could
The BBC Micro eclipsed the Spectrum in terms of technical capabilities Peter Johnson
only speak from a limited vocabulary. When the boss in Sinistar had finished building, it would laugh and say ‘I am complete!’, so when I cloned it in Deathstar I used the chip to make it say, ‘R R R, I an complete!’, which was the closest I could get. I bet it scared the life out of someone when they heard it do that for the first time.”
If anyone has any doubts as to how capable the Beeb was at recreating coin-ops, they only have to look at the early output from Acornsoft. They might have been unofficial, but titles like Planetoid (Defender), Snapper (Pac-man), Meteors (Asteroids) and Hopper (Frogger) provided
Beeb owners with an authentic arcade-at-home experience. Quality clones also came from Program Power (later Micro Power) who scored hits with Killer Gorilla (Donkey Kong), Mr Ee! (Mr Do!), Frenzy (Qix) and Bumble Bee (Lady Bug). And, of course, there was Superior Software which published a monsoon of coin-ops clones.
Having authored several games for Superior, Peter handled the official Beeb conversions of Yie-ar Kung Fu, Mikie and Arkanoid for Ocean’s Imagine label. “The BBC got such a reputation due to the amazing early work that Acornsoft did in replicating arcade classics of the time, setting an example for us all to follow,” he continues. “I always felt I should be aspiring to match the quality of its early titles with all my conversions.”
However, not everyone we spoke to felt that the Beeb was ideally suited for coin-op conversions. “It was only ever a middling fit for arcade clones,” says Nick Pelling, the celebrated author of Arcadians (Galaxian) and Zalaga (go on, guess). “Even though the graphics memory was nicely laid out, the amount of memory left over for squeezing code into was never really enough.”
Ah, memory. On 8-bit computers there was never enough RAM, and the Beeb suffered more than most. The Model A had just 16K so it was largely overlooked as a gaming platform. The Model B had 32K, which was preferable but still limited. “Memory was an issue, certainly,” admits Jonathan Griffiths. “We typically wanted a colourful screen, so that meant Mode 2, which was 20K of our 32K RAM gone immediately. And then the 6502 zero-page and stack was another 512 bytes. Finally, the BBC OS claimed a further 3K, so we were left with only 9.5K to craft our masterpieces. We had to use various tricks to claw back as much as we could. One example was in Geoff Crammond’s racing game Revs where he cunningly put bits
We were left with only 9.5K to craft our masterpieces, and that tiny budget included all our graphics Jonathan Griffiths
of the software in the screen display, in the sky area, by setting the palette entries for every pixel to be blue. That definitely shows that we had an issue with memory.”
Matthew Atkinson also struggled with the lack of RAM. “The standard machine was lacking in memory compared to some other computers,” he says, “but it could be circumnavigated to some extent by reprogramming the 6845 video chip to reclaim more memory in high-resolution colour modes. The BBC could have used an extra 16K in the ‘sideways’ RAM slot as standard. That would have been so liberating for programmers and led to better games.” The BBC B+ and Master series models did come with extra RAM, and a number of games would automatically detect it and deliver enhancements if present. However, the Model B remained the core machine and publishers understandably targeted that first and foremost.
While the memory was a hurdle to overcome, the consensus from the programmers was that the Beeb was a great machine to develop games for. Kevin Edwards says, “BBC BASIC had a built-in assembler that made it very easy to assemble and test your own 6502 code. All the top games were written in machine code and this was so easy to do with a standard Beeb – ideally with a floppy drive. The code assembled fast and could be tested within seconds. There was no need for external development machines or extra hardware. It also had a great keyboard which was important when you spent all day, coding.”
onathan Griffiths was also thankful for the assembler that was included within the machine’s BASIC interpreter. “It was a huge benefit. I taught myself 6502 assembler on the BBC’S predecessor, the Acorn Atom. That had the same combined BASIC and assembler, but crammed into just 8K rather than the 16K that the BBC had. Thanks to the extra space there was now floating-point arithmetic, nicer BASIC and an even better assembler. Because it was so easy to swap from BASIC to assembler and back, that made writing test fragments much easier.”
Matthew Atkinson is in agreement about the assembler. “It was fabulous for games development, providing the ability to mix assembler and BASIC, create macros and so on. I later did some development work on the Amstrad CPC, which was very similar in technical capabilities to the BBC, but much more difficult to use in this respect.”
ne of the thornier aspects of the era was the sheer number of unlicensed arcade clones. These could be found on most home computers, but the Beeb in particular was a hotbed of brazen clones. Jonathan Griffiths reveals that he and his coding colleagues, Neil Raine and Tim Dobson, were given free rein by Acornsoft, so they’d go out and play the latest coin-ops and then divvy up between them which ones they’d convert. And Jonathan can’t remember any significant problems arising.
“There were copyright issues with Snapper,” he says. “I changed the sprites and that fixed that problem. We got away with Rocket Raid, even though it was even more of a copy of Scramble than Snapper was of Pac-man.”
One theory as to why so many clones went unnoticed on the machine involves the BBC connection. Did copyright holders believe that the broadcaster was involved and thought twice about sending in the lawyers? Peter Johnson doesn’t think so. “This was common across all home computers, so I don’t think it was the BBC name that put them off. I was more likely that the Us-based companies didn’t notice at first as the BBC Micro wasn’t big in the States. The home computer market started out small, and it was a more naive time generally, with the finer points of what was covered by copyright or trademark laws still to be tested in court. My first game Q*bert received a cease and desist letter from Gottlieb after only a week or two on-sale, but that was because we were using the actual name. Several years of cloned games under different names followed – although how we never attracted a writ for using the word ‘Deathstar’ I’ll never know.”
Licencing issues aside, the fact remains that the BBC Micro was a fantastic platform for games. An interesting facet of this is that many gamers will have enjoyed these titles despite never actually owning an Acorn. You see, with BBC Micros present in so many classrooms, there would almost certainly be clandestine disks full of arcade games floating around, for those afterschool computer clubs where members wanted to play Killer Gorilla rather than Granny’s Garden. In this respect the not-so-studious BBC Micro served an edifying purpose, ensuring that our kids were well versed in dot munching, barrel jumping, alien destructing and other essential life skills.
It was fabulous for games development, providing the ability to mix assembler and BASIC Matthew Atkinson
» LEFT [BBC Micro] Acornsoft’s Rocket Raid was a very fine version of Konami’s landmark scrolling shooter Scramble. » ABOVE [BBC Micro] Monsters, heavily inspired by Space Panic, was an early hit for Acornsoft. » [BBC Micro] Matthew Atkinson’s...
» [BBC Micro] Simple Space Invaders clones were ten-a-penny on the Beeb. This is Invaders from IJK software. » [BBC Micro] Dunjunz was Bugbyte’s Gauntlet clone, although it did split the action across four screens. » [BBC Micro] Peter Johnson worked on...
» Jonathan Griffiths, developer of Snapper and Rocket Raid. » The prolific Peter Johnson wrote more than a dozen coin-op conversions for the Beeb.
» [BBC Micro] Before creating Repton, Tim Tyler wrote a version of Moon Patrol that was published by Superior as BMX On The Moon! » ABOVE [BBC Micro] Following a complaint, Jonathan Griffiths was forced to change the sprites in Snapper, his Pac-man...